In European Pat. No. 71,738 there are described a number of piperidine and piperazine containing theophylline derivatives as compounds having various pharmacological activities. Further, a number of 4-[1H-indol-3-yl]piperidines are described in U.S. Pat. No. 3,980,658 and in U.S. Pat. No. 3,947,578 as compounds useful as tranquillizers respectively as neuroleptics, and in U.S. Pat. No. 4,359,468 and U.S. Pat. No. 4,342,870 as anti-allergics and hypotensives respectively as serotonin antagonists. The compounds of the present invention differ therefrom essentially by the fact that they invariably contain a 1,3-dimethyl-1H-purine-2,6-dione moiety connected to a 1H-indol-3-yl substituted piperidine or 3,6-dihydro-1(2H)-pyridine, and by their specific pharmacological properties.